(1) Field of the Invention
The present invention relates to a ballast cleaning machine for excavating ballast from underneath a track and for receiving, cleaning and transporting the excavated ballast, which comprises a machine frame comprising two frame parts, each machine frame part having opposite ends, one of the ends of one machine frame part adjoining one of the ends of the other machine frame part while the machine frame part ends opposite to the one ends are remote from each other, and the adjoining machine frame part ends being pivotally linked to each other for pivoting about a vertical axis. Respective undercarriages support the machine frame on the track, two of the undercarriages being arranged at the remote machine part ends and a third one of the undercarriages being arranged on one of the machine frame parts in the range of the vertical pivoting axis. An endless ballast excavating chain is arranged on a first one of the machine frame parts, the chain including a transverse section extending for operation under the track, a ballast screening arrangement is arranged to receive excavated ballast from the chain, and a track lifting device is arranged on the first machine frame part adjacent the transverse ballast excavating chain section.
(2) Description of the Prior Art
U.S. Pat. No. 4,538,686, dated Sept. 3, 1985, discloses a self-propelled ballast cleaning machine which comprises a machine frame whose opposite ends are supported by undercarriages on the track. Arranged between the machine frame ends are an endless ballast excavating chain including a transverse section for operation under the preferably lifted track, a track lifting device and a ballast screening arrangement arranged to receive the excavated ballast from the chain. The track lifting stroke is limited by the two undercarriages at the opposite ends of the machine frame so that it may not be possible to lift the track sufficiently for accommodating the transverse chain section therebelow in track sections which have a relatively shallow ballast bed. On the other hand, a longer wheel base, which would enable the track lifting stroke between the undercarriages to be correspondingly increased, causes the endless ballast excavating chain to extend in track curves laterally beyond the track during movement of the machine between operating sites.
U.S. Pat. No. 4,538,687, dated Sept. 3, 1985, discloses a ballast cleaning machine comprising a tripartite machine frame, the adjoining ends of the machine frame parts being pivotally linked to each other for pivoting about vertical axes. The machine frame of this high-efficiency machine is supported on the track by undercarriages arranged at the remote ends of the two outer machine frame parts as well as in the range of the pivotal links of the outer machine frame parts with the intermediate machine frame part. The intermediate, bridge-like machine frame part carries an endless ballast excavating chain including a transverse section for operation under the preferably lifted track, a track lifting device and a high-capacity ballast screening arrangement arranged to receive the excavated ballast from the chain. A retractible auxiliary undercarriage is mounted on the intermediate machine frame part ahead of the ballast excavating chain in the operating direction of the machine for use only during movement of the machine between operating sites. A vertical adjustment drive for this retractible undercarriage is arranged in the range of the pivotal link between the intermediate and leading machine frame parts to enable the front end of the intermediate machine frame part with this undercarriage to be vertically adjusted with respect to the leading machine frame part and the track. In this way, the distance between the two undercarriages wherebetween the track lifting device is arranged may be increased during operation of the machine to insure sufficient lifting of the track. On the other hand, lowering of the retractible undercarriage into engagement with the track enables the machine frame to be properly supported on the track so that the machine may be incorporated into a train for movement between operating sites while assuring that the excavating chain will not unduly extend laterally beyond the track in sharp track curves. To enable the transverse ballast excavating chain section, which has a considerable height to increase its excavating capacity, to be inserted under the track even if the ballast bed is too shallow to permit a normal lift of the track, a continuously operating ballast tamping arrangement is mounted on the leading machine frame part to increase the height of the bed. This lifting of the track ties by tamping ballast under them ahead of the ballast excavation has been very successfully used in commercial track rehabilitation but requires the additional tamping stage. An increased lifting stroke can be effected by the track lifting device only if the undercarriages were spaced farther apart but this would cause the transverse chain section to extend unduly beyond the track in sharp curves.
U.S. Pat. No. 3,690,262, dated Sept. 12, 1972, relates to a track rehabilitation technology fundamentally different from ballast cleaning, i.e. it discloses a track correction and tamping machine with an elongated machine frame supported on undercarriages, the wheel base of the machine being extensible for improving the track lift during tamping and track repositioning. For this purpose, the tamping and track lifting unit is mounted between a rear and intermediate undercarriage, an additional front undercarriage being longitudinally and vertically adjustably mounted at a front end of the machine frame. During operation of the tamper, this front undercarriage is longitudinally displaced into a forward position and lowered into engagement with the track, while the intermediate undercarriage is lifted out of engagement with the track so that the track is freely movable at this point. This structure increases the track lifting stroke of the tamper lifting unit and enables additional ballast to be tamped under the ties.